Engines have long utilized a variety of devices that draw power directly or indirectly from the engine for their operation. Among these devices are fuel injectors, gas intake and exhaust valves, exhaust brakes, etc. In the past, these devices were typically actuated by a cam that is driven directly by the engine. In order to improve engine performance across its operating spectrum, there has been a trend in the industry toward the adoption of electronically controlled hydraulic devices. An example of this trend is the hydraulically-actuated electronically-controlled unit injector (HEUI) system utilized by Caterpillar, Inc., of Peoria, Ill., in their diesel engines.
In a typically HEUI system, a high pressure pump maintains a common rail containing engine lubricating oil at a relatively high pressure that is sufficient to actuate the hydraulic fuel injectors. The high pressure pump draws oil from a reservoir that is filled by the engines' low pressure oil lubrication circulating pump. After the high pressure oil is utilized by the fuel injectors, it is circulated back to the oil pan. Thus, a portion of the oil moved by the low pressure oil lubrication pump is circulated through the engine for lubrication, and another portion is pumped into the reservoir that supplies the high pressure pump.
In this current system, the high pressure pump is attached to the outside of the engine, and thus any noise emitted from the pump is easily detectable. In addition, the reservoir that supplies the high pressure pump is above the engine's oil pan. This can result in excessive engine cranking from a cold start while the low pressure pump provides enough oil to the reservoir for the high pressure hydraulic system to achieve the relatively high pressures necessary for its operation. Not only does the high pressure pump tend to emit noise, but its location on the outside of the engine creates a protrusion that undermines the ability to position the engine in a confined space. Finally, because the current system uses both a low and high pressure pump, there is generally a higher probability of failure than if the system could accomplish its tasks with a single pump.
The present invention is directed to these and other problems associated with engines that utilize hydraulically actuated devices.